Controlling the movement of an article is sometimes provided by a damper which is typically operably connected between the article and a stationary object. Upon exertion of a force on the article, movement of the article is restricted or controlled by the damper by providing a resistive force to the article.
Existing dampers are typically designed to operate in either a linear or rotational manner. Linear dampers frequently rely on linear mechanical engagement between components within the damper to provide the resistive force. Rotational dampers usually rely on a fluid between components within the damper to provide the resistive force or torque during rotation of those components.
Dampers, and particularly rotational dampers, can provide either constant or variable torque. A constant torque damper provides substantially the same torque regardless of the speed or acceleration of the article and is typically referred to as a brake.
A variable torque damper, however, provides increasing torque upon increasing speed or acceleration of the article. Accordingly, the speed of the article is controlled and preferably remains substantially constant as the article is subjected to a force providing the increasing speed which is desirable in many applications.
Fluid dampers usually rely on a damping medium, preferably silicone, positioned between two concentrically mounted members where the outer layers of the silicone become somewhat adhered to the members. During rotational movement between the members, shear is developed within the inner layers of the silicone which provides the desired resistive force or torque. An example of such a silicone damper is illustrated in U.S. Pat. No. 2,775,317.
Silicone or other fluid dampers, however, are susceptible to leakage which not only reduces the damping ability of the damper but causes damage to surrounding objects. The possibility of leakage is enhanced during use since heat is typically generated within the damper which thins the silicone.
It therefore would be desirable to provide a damper which does not rely on a fluid to provide the damping forces, which completely eliminate the risk of leakage and provides either a constant or variable resistive force or torque.